Liquid Fuels by Low-Severity Hydrotreating of Biocrude

Abstract

Biocrude (fast pyrolysis oil from wood) was hydrotreated to minimize the negative aspects of this fuel. The instability of the oil was reduced by reaction of the most unstable functional groups. Concurrently, the oxygenated component of the oil was also reduced, resulting in an improved energy density. Changes in the physical handling properties were also modified. All of this change was accomplished at less severe processing conditions (lower temperature, shorter residence time) than that required for the earlier processing for gasoline production. Improved conversion was achieved by the use of a downflow reactor system. The experiments reported include those performed with clean (filtered hot vapor) biocrude just recently available from processing systems in the U.S.

Mild hydrotreating of biomass pyrolysis oils to produce a suitable refinery feedstock

“…Significant work on the hydrotreating of biomass pyrolysis oil has been done in trickle-bed reactors [17,18] while mostly model compound studies [19,20] with very little work on whole oil [21,22] has been done in batch reactors. A semibatch configuration with hydrogen flow capability was chosen for this work.…”

“…Severity was then further increased by increasing temperature, hydrogen pressure, hydrogen flow rate, and catalyst-to-feed ratio. The stabilization temperature was also lowered to 1508C, because this is reported to reduce deactivation of the catalyst by coking [17]. Finally, a condition was selected for the large batch run.…”

A review of the chemical and physical mechanisms of the storage stability of fast pyrolysis bio-oils

“…In addition, an aqueous phase after hydrogenation contained significant amounts of organic compounds. Only after more extensive hydrogenation in the second-stage reactor, which reduced the oxygen content to less than 10%, was the viscosity of the product oil lower than that of the original biooil (Elliott and Neuenschwander 1997). Much of the initial oxygen reduction in the tar-like product was apparently due to the extraction of the polar oxygenated organic compounds by the aqueous phase from the tar phase, removing their viscosity-reducing (solvent) properties from the organic phase.…”

Combustion Properties of Biomass Flash Pyrolysis Oils: Final Project Report

“…Polymerization and condensation reactions involving the oxygen functionalities of the constituents of the oil lead to significant increases in the viscosity and water content of the oil over the course of weeks at room temperature and over the course of hours when maintained near 100"C . This property of biomass oils probably poses the most severe technical barrier to substantial commercial use of this fiel, Research has been conducted on hydrotreating bio-oils or cracking with a zeolite catalyst to remove the oxygen functionalities of the oil, but the process efficiency is poor and substantial technical barriers remain (Bridgwater and Cottam, 1992;Maggi and EllioK 1997;Elliott and Neuenschwander, 1997;Conti et al, 1997). The most promising approach to reducing the rate of aging of the oils is to use simple fbel additives, such as water or methanol (Diebold et al, 1996;Maggi and Elliott, 1997).…”